1. Field of the Invention
The present invention relates to an economical and safe method for producing on an industrial-scale specific δ-aminopentadienoate derivatives that are useful, for example, as UV absorbents.
2. Description of the Related Art
Methods of producing δ-aminopentadienoate derivatives have been known for a long time. For example, F. M. Harmer, Heterocyclic Compounds-Cyanine Dyes and Related Compounds (John Wiley & Sons, New York and London, 1964), Chapter XIII, page 491, and U.S. Pat. No. 2,165,339 and U.S. Pat. No. 2,186,608 disclose methods of producing δ-aminopentadienoate derivatives via dianil derivatives. However, the reaction path of the disclosed methods is long and the overall yield is low.
On the other hand, Tetrahedron Letters, Vol. 21, page 3155 (1980) discloses a method of producing δ-aminopentadienoate derivatives by reacting a streptocyanine derivative with a carbonyl compound in the presence of sodium hydride and triethylamine. However, sodium hydride is flammable, and therefore, the method is unfavorable for industrial-production from the viewpoint of safety, and in addition, the yield of such a method is not sufficiently high.
From the above background art, a method using safe reagents for producing the derivatives in a shorter reaction path is desired.